Radio-embolization of the liver is used to treat cancer of the liver, and entails deposit of radioactive beads in the liver to kill cancer cells while leaving the bulk of the liver intact. The beads, or microspheres, contain Yttrium 90 (Y90), which is radioactive and emits ionizing radiation (beta radiation, which penetrates only slightly through body tissue). This radiation kills nearby tissue, including cancer cells and viable liver cells. The Y90 is thus deposited only near a malignant liver tumor. Y90 has a short half-life (2.67 days), so it decays away fairly quickly and will not harm other areas of the body or other parts of the liver unless the microspheres used to deliver the Y90 flow immediately to unintended parts of the liver or the body.
To accomplish the therapy, a suspension of microspheres loaded with Yttrium 90 in a delivery fluid are injected by catheter into a blood vessel feeding the liver, or a small portion of the liver. The liver has a dual blood supply, being supplied with blood through the proper hepatic artery and the portal vein. The proper hepatic artery branches off the common hepatic artery, which in turn branches off the celiac artery which in turn branches off the aorta, to supply arterial blood to the liver. A catheter can be navigated to the proper hepatic artery and its branches starting through an access point in the femoral artery. The portal vein carries blood from the intestines to the liver. Radio-embolization of the liver is achieved through the hepatic artery, because it is easier to get to, and because most cancer in the liver is fed by the hepatic artery.
Radio-embolization entails deposition of numerous microspheres loaded with radioactive isotopes such as Y90. The microspheres cause blockage of the artery (embolization), with the effect of depriving cancerous regions of the liver of blood, while the beta radiation from the Y90 kills the cancerous cells. Though the hepatic artery is blocked, blood supply to the liver is provided through the portal vein, and the liver may quickly re-vascularize with new arteries arising from the hepatic artery and other nearby arteries.
In some cases, clinicians have taken to embolizing nearby extra-hepatic arteries, such as the arteries branching off the common or proper hepatic artery (gastroduodenal and supraduodenal arteries, for example), to prevent reflux of microspheres intended for the liver to unintended locations such as the intestines or spleen. The supraduodenal artery, for example, is proximal/upstream to the liver, so that the entire proper hepatic artery can be occluded with Y90 microspheres while protecting this artery. These upstream branch arteries are embolized with numerous coils or one large coil, deposited by catheter, through the same access pathway used to deliver the microsphere. This technique is demonstrated in Lopez-Benitez, Protective Embolization of the Gastroduodenal Artery with a One-HydroCoil Technique in Radioembolization Procedures, 36 Cardiovascular Interventional Radiology 105 (2013). As stated in this article, complete occlusion of the gastroduodenal artery can take over 30 minutes, and sometimes cannot be achieved. Since coil placement, flow monitoring to detect occlusion, and subsequent microsphere deposition are all visualized under fluoroscopy, the long time to accomplish occlusion thus represents a significant additional exposure to fluoroscopy for the patient and clinician, and a significant increase in the time to accomplish the radio-embolization procedure. The un-occluded length of the extra-hepatic artery not occluded by the coils can lead to recanalization and gastro-intestinal complications from radiation induced ulceration. Also, the coil implantation has not been effective in limiting recurrence and metastasis after trans-catheter arterial embolization.
In our prior U.S. patent, Strauss, et al., Embolic Implant And Method Of Use, U.S. Pat. No. 8,641,777, (Feb. 4, 2014) we disclosed an embolic implant for use in neurovascular applications. This implant provides immediate occlusion and stoppage of blood flow when deposited in a blood vessel. Though a summary of the devices disclosed is provided below, we incorporate by reference the entire disclosure U.S. Pat. No. 8,641,777.
The implant comprises a wire frame structure including a pair of opposing zigzag segments including a plurality of V-shaped elements defining an open end, with the V-shaped elements joined at the open end of the V-shaped elements via short longitudinally aligned struts to form a central portion of the wire-frame structure and a plurality of longitudinally oriented struts extending from the proximally pointing vertices of the V-shaped elements and joined together near the radial center of the wire-frame structure at the proximal end of the embolic implant. The wireframe structure is formed of a self-expanding material. A blood impermeable membrane is disposed over the one end of the embolic implant, and has a proximal facing surface, such that blood is substantially prevented from flowing through the implant when deployed in the parent artery.
The embolic implant can be used to improve a radio-ablation of the liver.